Use your knowledge of argument forms and the counterexample method to determine which, if any, of the following statements are true.
a. If you can give a substitution instance with true premises and a false conclusion, then this will show that an argument form is invalid.
b. In the form for a hypothetical syllogism, the letters represent noun phrases.
c. To be a counterexample, a substitution instance must use terms or statements that begin with the same letters as those in the argument form of which it is an instance.
d. All invalid arguments are substitution instances of the same form.
e. In all argument forms, the letters represent statements.
f. A single counterexample is enough to prove that an argument or an argument form is invalid.
g. A counterexample can demonstrate why the conclusion of an argument does not follow by necessity from the argument's premises.